This invention relates to new and useful improvements in orthodontic arch wires.
Arch wires are commonly used in orthodontic procedures in cooperative association with other components, typically brackets and buccal tubes. An arch wire is disposed on the labial side of the arch, and when connected to brackets and tubes on teeth of the arch, it serves to develop corrective forces for performing tooth movement.
Typical arch wires are a high quality stainless steel. They have either a circular transverse cross section or a rectangular transverse cross section.
Typical usage of metallic orthodontic components renders their presence apparent to others in the individual wearer's every-day activities.
In order to make orthodontic appliances more aesthetically pleasing, efforts have been made to render them less noticeable. An example of this is contained in U.S. Pat. No. 4,302,532 in which translucent plastic brackets are disclosed. The arch wire, however, has continued to be stainless steel wire and therefore, the use of plastic brackets does not provide a complete aesthetic solution. It is believed that a plastic arch wire would be generally incapable of performing orthodontic treatment procedures in the same manner as a stainless steel equivalent. An example of a plastic arch wire is shown in U.S. Pat. No. 4,585,414. It is said to possess substantially greater flexibility and resilliency than a stainless steel arch wire of the same diameter, thereby confirming the foregoing suspicisions about its equivalence to stainless steel.
The present invention relates to new and improved forms of orthodontic arch wires which possess the force tranmitting and physical performance characteristics of conventional stainless steel arch wires yet, which can also be rendered aesthetically pleasing so that the presence of the arch wire is much less noticeable than in the case of a conventional stainless steel arch wire.
Briefly, the present invention in its generic aspect comprises the selective coating of a metal arch wire with an outer covering of a non-metallic material, such as plastic, by a co-extrusion process such that the labial side of the arch wire is covered by non-metallic material which is colored to match the individual's teeth thereby rendering the presence of the arch wire much less noticeable than would be the case where the arch wire is entirely stainless steel, yet the plastic does not encapsulate the full transverse cross section of the arch wire but rather leaves that portion of the arch wire which bears against the brackets free of non-metallic material so that the steel wire itself bears against the brackets.
Further aspects of the invention relate to particular details of the transverse cross sections and a number of embodiments of such cross sections are disclosed. As will be seen, these various cross sections have particular features which are beneficial and which provide further enhancements to the manufacture and effectiveness of the arch wires.
In addition to the improved aesthetic benefit attainable with the invention and the functional benefit of metal-to-metal contact between the arch wire and brackets, there is a further functional benefit in that the inclusion of the non-metallic material on the metal of the arch wire can in certain cases provide a protection to the mouth of the individual wearer. In this regard, a commercially available product known as the "Soft Sleeve" is used to provide protection against an arch wire causing irritation to the mouth of the individual wearer. The "Soft Sleeve" is a separate piece of cylindrical tubing which is inserted onto an arch wire to a desired location of placement. It is often used incidental to a tooth extraction.
The present invention can perform the same function as the "Soft Sleeve" but without the need to have a separate sleeve inserted onto the arch wire because the arch wire of the present invention inherently contains non-metallic material on those portions of the arch wire which might in certain individuals induce irritation in adjacent soft tissue. Moreover, unlike both the "Soft Sleeve" and the plastic arch wire of U.S. Pat. No. 4,585,414, the present ach wire is capable of formation into commonly used orthodontic loops and bends.
The foregoing features, advantages and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.